The present invention relates a fastening element for the connection of two sheets or plates (herein termed sheets) arranged at a selectable angle in relation to each other along their abutting edges using two gripping jaws able to be centrally connected with each other by means of a screw, said jaws having wings of different length and forming two bearing sockets, in each of which there is rotatable cylindrical gripping rollers provided with an axial gripping groove and consisting of elastic material.
Such a fastening element for the connection of sheets placed adjacent to each other at selectable angles along their abutting edges with joint parts of elastic material has already been proposed in the German Pat. No. 1,933,378, in the case of which the joint parts have two separate gripping rollers each provided with an axial gripping groove and having a circular cylindrical form, such rollers being borne in two gripping jaw halves able to be connected together by means of a screw and forming bearing sockets in such a manner that the same are able to be freely turned into the condition in which they are not screwed together.
However such a known arrangement has the disadvantage that it is difficult to set the sheets at the desired angle to each other, since it is hard to align the sheets during assembly prior to screwing tight the screw with the gripping rollers only loosely mounted in the bearing sockets of the gripping jaws in which the rollers are able to freely turn. If for instance the sheets are boards to be erected as part of an exhibition booth so as to comply with a specific geometry, as for instance a polygon, it is only possible for the configuration to be achieved exactly if the included angle between two adjacent sheet is so exactly set that it complies with the desired geometrical configuration to be produced.
In this respect it is a disadvantage as well that the gripping groove in the gripping rollers has a form of cross section which is rectangular and tapers towards the open end since this means that this gripping groove in the gripping rollers is hard to open out for assembly on the sheets in order to attach the gripping rollers on the sheets, since the assembly operator would have to then have both hands free and this would mean that he would not be able to work quickly enough.
A further disadvantage is that each of the gripping rollers separately mounted in each of the bearing sockets are quite likely to drop out of the bearing sockets and be lost during assembly of the fastening element, so that the assembly of the element is impeded.
A further disadvantage is that if the gripping effect of the rollers should slacken off somewhat the sheets are no longer held fast in the fastening element and may come out of the fastening element.
A still further shortcoming in this known arrangement with gripping rollers in the known system is that it is only possible to connect sheet-like members together and parts with a different cross section are not able to be connected.